Position sensors include devices that generate change to an electronically interrogated physical parameter based on movement of a structure, such as, for example, an actuator shaft operatively coupled to the sensor. For non-contacting sensors, this change is achieved without physical contact to reduce fatigue failures or system degradation due to sensor drag or noise as desired for certain applications. In encoder devices, the physical parameter movement results in the generation of an electronic code representative of position or movement.
In most non-contacting sensor applications, it is often desired that the absolute position of the interrogated structure be provided within a pre-defined measurement range upon the application of electric power. It is also often desired that the position information be accurate and increment in a known linear fashion. Many electronically interrogated non-contacting properties have been applied to achieve such position sensing including, for example, light detection, magnetism, capacitance, inductance, and RF transmission.
In the area of rotary position sensing, particularly over a measurement range of 360 degrees, optical encoders are common. Optically based sensors typically employ an illumination source and an array of reflective or transparent coded segments and corresponding light-sensitive detectors. Optical sensors often suffer from limitations in operating temperature, and susceptibility to contamination and light source aging. In addition, to provide access to position information commensurate with the application of electric power, complicated encoder structures or multiple sensors have resulted that usually increase the cost and overall size of the sensor package. Accordingly, optical solutions are often executed as incremental encoders that count in precise units once a known position is detected within the encoded pattern. This type of sensor generally cannot provide position information with the immediacy desired unless enhanced by electronic memory, a secondary absolute position sensor input, or the like.
Thus, there continues to be a need for further contributions in this area of technology.